Common ink-jet printers print in the vertical plane; that is, paper is fed up through the print zone by means of a drive roller onto a platen. The paper is vertically stacked in an output tray.
In a radical shift from printing in the vertical plane, new ink-jet printers are under development which print in the substantially horizontal plane. Typically, paper is fed from an input paper tray through the print zone by means of a drive roller onto a platen. In this configuration, the paper is horizontally stacked in an output tray.
Such horizontally-printing ink-jet printers must deal with the problem of ink drying, unless specially coated paper is employed. If no mechanism is provided for drying the ink, then, with rapid output of paper, one sheet is placed in the paper output tray before the ink on the sheet underneath has had a chance to dry, thereby causing smearing of the print on the lower sheet.
One common mechanism is to provide some sort of drying means, such as a lamp or heater. However, such a requirement also adds to the complexity of the printer, since a power source, lamp or other heating device, and associated apparatus must be provided. Such apparatus also adds to the weight and cost of the ink-jet printer.
One approach to avoid the foregoing problems is to provide a passive drop scheme. In this approach, paper emerging from the print zone of the printer is guided along rails that suspend the paper above the output tray. At the completion of printing, the paper simply drops of its own weight into the paper tray, with the previously-printed sheet underneath having had an opportunity to air-dry during the printing of the next sheet.
While this is a satisfactory approach, it experiences occasional hang-ups, due to a phenomenon known as cockling. As is well-known, paper printed on one side cockles; that is, it becomes corrugated and stiff. As a consequence, rather than dropping into the output tray, the paper tends to get pushed off the rails onto the printer stand or floor by subsequent sheets. This cockling effect becomes more pronounced with environmental extremes and large amounts of ink on the paper.
It is desired to reduce the cost and complexity of handling paper with wet ink generated by ink-jet printers, while simplifying the components and their interactive association. It is also desired to handle paper stacking problems created by paper cockling.